/* ==========================================
 * JGraphT : a free Java graph-theory library
 * ==========================================
 *
 * Project Info:  http://jgrapht.sourceforge.net/
 * Project Creator:  Barak Naveh (http://sourceforge.net/users/barak_naveh)
 *
 * (C) Copyright 2003-2011, by Barak Naveh and Contributors.
 *
 * This library is free software; you can redistribute it and/or modify it
 * under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 2.1 of the License, or
 * (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
 * or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
 * License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this library; if not, write to the Free Software Foundation,
 * Inc.,
 * 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
 */
/* -------------------
 * StarGraphGenerator.java
 * -------------------
 * (C) Copyright 2011-2011, by Assaf Mizrachi and Contributors.
 *
 * Original Author:  Assaf Mizrachi
 * Contributor(s):   -
 *
 * $Id: GridGraphGenerator.java 1258 2013-04-18 20:27:18Z freecode4susant $
 *
 * Changes
 * -------
 * 3-Jan-2011 : Initial revision (AM);
 *
 */

package org.jgrapht.generate;

import org.jgrapht.Graph;
import org.jgrapht.VertexFactory;

import java.util.Map;
import java.util.TreeMap;

/**
 * Generates a bidirectional <a
 * href="http://mathworld.wolfram.com/GridGraph.html">grid graph</a> of any
 * size. A grid graph is a two dimensional graph whose vertices correspond to
 * the points in the plane with integer coordinates, x-coordinates being in the
 * range 0,..., n, y-coordinates being in the range 1,...m, and two vertices are
 * connected by an edge whenever the corresponding points are at distance 1.
 * Vertices are created from left to right and from top to bottom.
 *
 * @author Assaf Mizrachi
 * @since Dec 29, 2010
 * @param <V>
 * @param <E>
 */
public class GridGraphGenerator<V, E> implements GraphGenerator<V, E, V> {

    /**
     * Role for the vertices at the corners.
     */
    public static final String CORNER_VERTEX = "Corner Vertex";
    private final int rows;
    private final int cols;

    /**
     * Creates a new GridGraphGenerator object with rows x cols dimension.
     *
     * @param rows the number of rows
     * @param cols the number of columns
     */
    public GridGraphGenerator(final int rows, final int cols) {

        if (rows < 2) {

            throw new IllegalArgumentException("illegal number of rows (" + rows
                                               + "). there must be at least two.");
        }

        if (cols < 2) {

            throw new IllegalArgumentException("illegal number of columns (" + cols
                                               + "). there must be at least two.");
        }

        this.rows = rows;
        this.cols = cols;
    }

    /**
     * {@inheritDoc}
     */
    @Override
    public void generateGraph(final Graph<V, E> target, final VertexFactory<V> vertexFactory,
                              final Map<String, V> resultMap) {

        final Map<Integer, V> map = new TreeMap<>();


        // Adding all vertices to the set
        int cornerCtr = 0;

        for (int i = 0; i < (rows * cols); i++) {

            final V vertex = vertexFactory.createVertex();

            target.addVertex(vertex);
            map.put(i + 1, vertex);

            final boolean isCorner = (i == 0) || (i == (cols - 1)) || (i == (cols * (rows - 1)))
                                     || (i == ((rows * cols) - 1));

            if (isCorner && (resultMap != null)) {
                resultMap.put(CORNER_VERTEX + ' ' + ++cornerCtr, vertex);
            }
        }


        // Iterating twice over the key set, for undirected graph edges are
        // added from upper vertices to lower, and from left to right. The
        // second addEdge call will return nothing; it will not add a the edge
        // at the opposite direction. For directed graph, edges in opposite
        // direction are also added.
        for (final int i : map.keySet()) {

            for (final int j : map.keySet()) {

                if ((((i % cols) > 0) && ((i + 1) == j)) || ((i + cols) == j)) {

                    target.addEdge(map.get(i), map.get(j));
                    target.addEdge(map.get(j), map.get(i));
                }
            }
        }
    }
}

// End GridGraphGenerator.java



